## College Algebra 7th Edition

$x=\pm\sqrt{a}$ or $x=\pm2\sqrt{a}$
$x^{4}-5ax^{2}+4a^{2}=0$ $(a-x^{2})(4a-x^{2})=0$ $a-x^2=0$ or $4a-x^2=0$ $x=\pm\sqrt{a}$ or $x=\pm2\sqrt{a}$ (We can take the square root of $a$ because it is positive.)